A group of eight senators is asking the FDA to cease consideration of the fish as food, and is threatening to pull funding for the study if the agency does not comply.

An unmodified salmon, front, and one of AquaBounty Technologies'… (AquaBounty Technologies…)

Reporting from Washington — A group of senators has asked the Food and Drug Administration to abandon its approval process of genetically engineered salmon as food, threatening to push legislation to strip the FDA's funding to study the fish if the agency does not comply.

Eight senators sent a letter dated July 15 to the FDA asking it to "immediately cease" consideration of such salmon, a product brought before the agency by AquaBounty Technologies 15 years ago.

AquaBounty's proposal calls for the embryos of the fish to be sterilized in Canada before being shipped to Panama, where the males would be exposed to estrogen and sex-reversed. If the FDA rules in favor, the salmon would become the first genetically modified fish approved for human consumption.

The senators, who represent coastal states with thriving fisheries such as Alaska, Oregon and Washington, pledged not to provide funding for the program should the FDA go forward with the approval process. They argue that genetically modified salmon could kill jobs by interfering with the fish farming industry, cause environmental damage and potentially harm consumers.

"I just don't see a reason from a fundamental standpoint why we have to start manufacturing 'Frankenfish' when we have incredible fisheries that employ thousands of people," said Sen. Mark Begich (D-Alaska).

The senators' request comes a month after the House passed an amendment, by voice acclamation, to an appropriations bill that would strip the FDA of funding for the salmon program. Fifteen House members also signed a letter sent to the agency.

FDA spokeswoman Siobhan DeLancy said the agency would respond to the letters. There is no timeline for the FDA to complete an environmental impact assessment on the salmon, which it has been working on since September. Industry officials also are pushing back. They plan to send a letter to leaders in the House and Senate next week in defense of science-based regulation.

Although the fish would be kept in a land-based facility, environmental groups worry that the salmon could escape and potentially harm fish in the sea. They're also concerned that the fish, which do not get any larger than unmodified salmon but grow twice as fast, could out-compete native populations for food.

An AquaBounty spokeswoman said it's a common practice in fish farming to make the entire stock one gender to discourage breeding, even though the fish are rendered infertile.

Some opponents also are concerned about the possibility of the salmon breeding with nonmodified salmon. Although the genetically engineered fish would undergo sterilization, a small percentage could remain fertile, scientists say.

Other scientists contend that even if the cold-water fish did escape from the facility in Panama, they would die in warm water as they attempted to make their way downstream to the ocean.

"Even if someone were to steal and release them into the ocean of Panama, they would have to swim thousands of miles to find mates," said Bill Muir, a professor of animal sciences at Purdue University who specializes in genetics and environmental risk assessment, particularly of fish. Muir said he's looked at AquaBounty's product and deemed it safe for the environment.

But now that lawmakers have entered the debate, it appears the critics of the modified salmon are winning out. Begich pointed to a lack of transparency in the approval process, noting that the FDA almost approved the fish last fall without much public notice. Ronald Stotish, chief executive of Waltham, Mass.-based AquaBounty, dismissed the senator's concerns, arguing that the debate should be left to scientists.

"It would be a dangerous precedent to react to a handful of legislators' misinformed paranoia," he said in a statement. "The real waste of taxpayer dollars would be to abandon the important American principle of science-based regulation, responding instead to economics' protectionist fears or subjective and emotional judgments."